Capri V6 - Ignition failure/cut-out problem

allanv6gt · 09-11-2010, 10:40 PM

Okay, finally screwed all the bit back together after far too many years and am now having occasional (but unpredictable) complete failure of ignition circuit. Cranks over fine, just fails to fire. Appears to be plenty of fuel in carby.
It is as if circuit is getting earthed, but I don't have my security cut-out switch fitted yet.

Happens...
- sitting at the traffic lights
- around bends
- on a nice straight road
- after going thru a roundabout
...just anytime anywhere.
.......... but always after things have warmed up.

I've already changed the coil for a brand new one, and at rebuild I fitted a new ballast resistor on the coil and condensor in the distributor.

Before tonight, in the massive 200 miles since full rebuild, you could just switch off and restart ok in 10-15 seconds , usually before you stopped rolling. Tonight I was stranded for 5 mins each time. Suspect something needed to cool down.

So, dumb question time, causes anyone?

Possibilities so far include:
- broken ignition circuit wire somewhere, with circuit broken when car vibrates
- HT lead from distributor to coil (but getting total failure not misfire)
- faulty ignition switch (rekeyed at $$$ for new keys), that needs to cool down to work again
- loose ignition circuit wire under the dash
....and other things.

And, a super dumb question......(many years rebuild brain fade )
.........Does ballast resistor connect to positive or negative of coil?
(at least remove that mis-wire possibility)

Suggestions welcome, thanks.

T3man · 09-11-2010, 10:46 PM

Ballast to positive side of coil - the resistor is to reduce the voltage from 12 to 6.

I expect your problem to be the coil. I know you said you replaced it but ... three things can still be the problem.

1. Is the coil definitely a 6V one?

2. Is the ballast definitely reducing voltage to 6?

3. On very rare occassions even a brand new coil can be faulty - try another one that is known good (ie be working on a car).

Blown66 · 10-11-2010, 12:47 AM

T3man I think it might be 9 volts to the coil.

Are you still using points in your V6 ??

I would be taking a multi meter out next time you go out for drive & when it shuts down leave the key in the on position & check the voltage at the coil to see if the resistor is shagged.

caprispecial · 10-11-2010, 09:17 AM

If you were to hot wire it (positive wire from battery direct to + side of coil) and then went for a drive, if the problem is fixed then you know it is a faulty supply to coil. If not fixed then it is something else.
The capri has a resister wire built into the wiring loom its the pink wire connected between the tacho and left bulkhead connecter. This delivers a reduced voltage to the + side of coil so no need for fitting a ballast resister.
The coil should be a 12volt ballast type coil.

T3man · 10-11-2010, 11:13 AM

Yes it is a 12v coil.

According to the wiring schematics there is no external resistor, and 12v is supplied to the coil at all times. There is however a "ballast resistor" which is not a resistor at all and is purely a solenoid/relay to ensure that 12v is fed directly to the starter motor and the coil during cranking.

So, if you have tested the circuit and are sure there is 12v at the coil at all times then it comes back to two things IMO - coil is failing or condensor is failing.

caprispecial · 10-11-2010, 12:20 PM

T3man the schematic simply doesnt explain every detail, however if you look in the manual under Ignition it is explained there.
So the pink resistor wire is connected to a white yellow wire that plugs to the + side of the coil. This should deliver around 8 volts with the engine running. The idea of the reduced voltage is to stop the points burning.
At cranking however a full 12 volts is delivered to the coil via the starter soleniod momentarily to get the engine started.
Finding the problem will be by a process of elinination which is why I mentioned to hotwire it.

T3man · 10-11-2010, 01:25 PM

Yes, I think you are spot-on because my (old) memory always had me thinking it was definitely less than 12 volts at the coil - and the manual does explain it (vaguely) but gives no actual specifications for the correct operating voltage that I could find. I guess I thought it was 6 volts because that was the norm in those days and I had heaps of vehicles (including my Eskies) that had resistors/coils.

allanv6gt · 10-11-2010, 08:01 PM

Thanks peoples....

Pls note the Capri V6 engine bay wiring loom is different to the Capri 4 cyl (I know this from hard experience). The 4 cyl does indeed have the seperate starter solenoid and resistor. I did not find this anywhere on the V6 wiring (again , hard won experience). If anything, this feature must be part of the starter motor/solenoid arrangement on the V6 - which does have a direct battery feed to the starter (fat wire), with solenoid triggered by the ignition start circuit (skinny wire) .

Points - still using, have not got around to fitting the Lumenition yet. And the old car ran fine under this arrangement.

'Ballast resistor' - currently on positive side of coil. One wire to +, and earthed (?) to coil holder. But I thought this was how it was on the donor car - wanted to check.

Coil is almost new (400miles) and is a Bosch brand from a reputable parts shop (so probably not at fault). This was my first problem elimination step - to swap out the old unknown quantity coil with this (hopefully) more known state item.

Condensor is new-ish. But the current motor and ancillaries came out of the other just-a-goer-but-very-ugly shell. So....possibly. And is also a cheap item to simply swap in a new one.

I'll start checking voltages at certain points as suggested.
Bound to be something simple, just need to find it.

Once again, thanks.

caprispecial · 10-11-2010, 08:44 PM

allanv6gt if your ballast resister is wired from +side of coil to earth then thats maybe the problem, it should be wired one end to the wire from the ignition switch and other end to + side of coil.
But as has been said the v6 has the resistance built in to the pink wire from the ignition making the added resister block unnessesary.
To check this just remove the resister block and see how it runs. Then use the multimeter to check that the voltage to the + side of the coil is indeed reduced. (should be about 6-8 volts). Hope this helps.

T3man · 10-11-2010, 10:11 PM

Can you post a pic of your ballast resistor by any chance? It definitely shouldn't be earthed - it has to be in series as described by caprispecial.

A new coil can still be faulty no matter how reputable the seller is, nor what brand of coil either for that matter. But the more you post the more it sounds like a primary circuit wiring issue.

allanv6gt · 11-11-2010, 09:27 PM

The 'ballast resistor' has only one wire coming out of the 'can'. My term 'earthed' was merely to indciate that the tab on the 'can' is screwed to the handy lug on the coil holder strap. (Still with me). It is not at all like the 4cyl furse-clock style resistor. if anything , general appearance resembles the condensor inside the dizzy (i.e. a 'can' with only one wire comin' out!)

If it is any help, the ugly beasst was running one for 10yrs under this arrangement, but the wire fell off during the heart transplant into this shell. And the much-shortened wreck that came =with this good shell also had one fitted to the coil in tis manner. So... was just trying to cinrm I had out things back together, now that my 'model' layout was disturbed during the transplant operation.

An d yes, Primary igfnition circuit is my guess. After I check the basic wires for contiuity, I might try swapping in another igntion switch. My wifes Mazada 808 has a similar problem....just driving down the road - quite random.

T3man · 11-11-2010, 11:12 PM

That doesn't sound like a ballast resistor to me - it is most likely a suppressor and connects between the + coil terminal and earth to stop the pulses from the coil causing radio interference. It has nothing to do with why you are losing IGN - look elsewhere.

allanv6gt · 12-11-2010, 05:28 PM

Thanks T3man......doesn't look like what I would call a resistor either.
....And I will look elsewhere.

Coincidentally, the low-speed fan ciruit has ceased working since assembly (did work, not now)....and it is a true 'resistor' type arrangement. Easy swap ...once you get the parcel shelf out. I wonder ?

allanv6gt · 20-11-2010, 09:08 PM

Todays activites to resolve the problem:
1. Fit new (and bigger) condensor to distributor......ignition failed when hot.
Found 0 volts on inout to coil, so disconneted raid suppressor condensor. and restarted fine.
2. zoomed around the block 2 timnes ....and it cut out just after a slight bend. Restarted after OK 10 secs........so not distributor or raadio noise suppressor.
3. Ratted the old ignition switch out of the ugly shell (because it was working fine when the thing was mobile) with the intent of doing a quick switchover job to a known-working Ign switch.
Removed the parcel shelf in the pretty shell (always fun !!).
Pulled off trim around ignition switch and found.....the nice grey wiring loom plug was not fully attached to the ignition switch. ..........DOH !!! Enough tab was visible to explain intermittency as things move around with car motion.
Pushed it all the way back on and reassembled. Just finished this task, so I'll be brave and do some more laps around the block tomorrow and see if I get stranded.

Sometimes life is just too busy to spend the time looking for the simple solutions......methodically.
These cars are soooo simple, it should be easy to find these types of problems. Just need the patience and some decent dedicated time to work thru things.

My level of intimacy with the beast has proven it's worth and not try to hurry things.

Will report back on outcome.

cosworthfreak · 20-11-2010, 10:05 PM

Always satisfying to find a solution to a problem (despite the frustration on the way).

Hopefully you've found the cause.

allanv6gt · 23-11-2010, 08:08 PM

Outcome - FIXED !!!!!! (cross fingers)......
Appears to have been half disconnected ignition switch inside the cowling.

Been going around and around the suburb for the last 40 mins. Electrical gremlin seems to have emigrated to someones elses car......

Sooooo.............
Put it together,
Go and check your connections again......
Dont rush it,
Be patient,
Don't get too excited (just because it has been 20yrs...),
Expect some niggles,
Test drive close to home (so as not too far to walk for tools/ towrope),
And if you need to pull it apart again, go back to top of this list !!